Irradiance Power-Area Cross-Scan - Electromagnetic Radiation Pressure and Momentum Step by Step

Irradiance is scanned across source power and beam area. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

Irradiance is the source quotient

The displayed irradiance comes from one checked power field and one checked beam-area field.

I=P/A=24/4=6\ \text{W}/\text{m}^{2}

Changing power changes irradiance directly

Beam area is fixed in these rows. The irradiance column rises only because the source power rises.

\begin{array}{c|c|c}P&A&I\\12\ \text{W}&4\ \text{m}^{2}&3\ \text{W}/\text{m}^{2}\\24\ \text{W}&4\ \text{m}^{2}&6\ \text{W}/\text{m}^{2}\\36\ \text{W}&4\ \text{m}^{2}&9\ \text{W}/\text{m}^{2}\\\end{array}

Changing beam area changes irradiance inversely

Now power is fixed. Larger beam area spreads the same power into a smaller irradiance.

\begin{array}{c|c|c}P&A&I\\24\ \text{W}&3\ \text{m}^{2}&8\ \text{W}/\text{m}^{2}\\24\ \text{W}&4\ \text{m}^{2}&6\ \text{W}/\text{m}^{2}\\24\ \text{W}&8\ \text{m}^{2}&3\ \text{W}/\text{m}^{2}\\\end{array}